Piezoelectric ceramics

ABSTRACT

PIEZOELECTRIC CERAMICS ARE PROVIDED CONSISTING ESSENTIALLY OF A SOLID SOLUTION OF PB(FE1/2SB1/2)O3, PBTIO3 AND PBZRO3 WHERE UP TO 25 ATOM PERCENT OF PB MAY BE REPLACED BY AT LEAST ONE BA,SR AND CA AND MANGANESE OXIDE IN THE AMOUNT OF 0.10 OT 3.0 WEIGHT PERCENT IN THE FORM OF MNO.

April 4, 1972 TQ MEJ| QHNQ ET AL 3,654,160

PIEZOELECTRIC CERAMICS 2 Sheets-Sheet 1 Filed July 10, 1969 FVIG.I

INVENTORS TOM EJI OH N O United States Patent Office Patented Apr. 4, 1972 The portion of the term of the patent subsequent to Dec. 30, 1986, has been disclaimed Int. Cl. C04b 35/46, 35/48 US. Cl. 252-623 3 Claims ABSTRACT OF THE DISCLOSURE Piezoelectric ceramics are provided consisting essentially of a solid solution of Pb(Fe Sb )O PbTi and PbZrO where up to 25 atom percent of Pb may be replaced by at least one of Ba, Sr and Ca, and manganese oxide in the amount of 0.10 to 3.0 weight percent in the form of MnO.

This invention relates to piezoelectric materials and more particularly to piezoelectric ceramics having excellent piezoelectric properties.

This application is a continuation-in-part of application Ser. No. 688,431 filed Dec. 6, 1957, now Pat. 3,487,- 091 issued Dec. 30, 1969.

BACKGROUND OF THE INVENTION The fundamental measures for evaluating the piezoelectric properties of a piezoelectric material are the electromechanical coupling factor and the mechanical quality factor. The former is representative of the efficiency of transforming electrical oscillation into mechanical vibration and of conversely transforming mechanical vibration into electrical oscillation A greater electromechanical coupling factor indicates for better efiiciency of interconversion. The latter factor shows the reciprocal proportion of the energy consumed by the material during the energy conversion, a larger mechanical quality factor indicating smaller energy consumption.

One of the typical fields for application of piezoelectric materials is in the manufacture of elements for ceramic filters. In this case, it is desirable to provide an electromechanical coupling factor with an optimum value selected from a wide range between the extremely great and the very small while the mechanical quality factor should assume as large a value as possible. This fact is vfully described in, for example, R. C. V. Macario, Design Data for Band-Pass Ladder Filter Employing Ceramic Resonators which appears in Electronic Engineering, vol. 33, No. 3 (1961), pp. 171-177.

The transducer elements of mechanical filters provide another important field for application of piezoelectric ceramics. In this case, both the electromechanical coupling factor and the mechanical quality factor should be as large as possible.

In a copending application, U.S. Ser. No. 688,431 now Pat. No. 3,487,019, filed by the same applicant, there is disclosed novel piezoelectric ceramics of Pb(Fe Sb )0 PbTiO -PbZrO Although these ceramics have a remarkably large electromechanical coupling factor, the mechanical quality factor is low and hence the fields of application are ratherirestricted. They are not suited for use in the manufacture of elements for ceramic filters and transducer elements for mechanical filters.

OBJECTS OF THE INVENTION The object of this invention is to provide piezoelectric ceramics having high values for both the electromechanical coupling factor and the mechanical quality'factor.

Another object of this invention is to provide piezoelectric ceramics suitedfor use in fields such as the manufacture of elements of ceramic filters and the transducer elements of mechanical filters.

SUMMARY OF THE INVENTION This invention is characterized by ceramic compositions consisting essentially of a solid solution of ternary system and manganese oxide ranging from 0.10 to 3.0 percent weight. The lead (Pb) contained in the basic Pb(Fe Sb )O -PbTiO -PbZrO composition may be replaced, up to 25 atom percent thereof, by barium (Ba) strontium (Sr) or calcium (Ca).

Where the basic Pb(Fe Sb )O -PbTiO -PbZrO composition is represented by the compositional formula where x, y, and z are a set of mol ratios and x+y+z= 1.00, the composition should be restricted within the range determined by the following combinations of the mol ratios x, y, and z:

Incorporation of manganese oxide (MnO) in the amount of 0.10 to 3.0 weight percent into the basic composition mentioned above improves the mechanical quality factor without fatal decrease in the electromechanical coupling factor and produces useful piezoelectric ceramics applicable to the elements of ceramic filters and the transducer elements of mechanical filters.

BRIEF DESCRIPTION OF THE DRAWINGS DETAlLED DESCRIPTION Examples Powdered materials of lead monoxide (PbO), ferric oxide (Fe C antimony sesquioxide (Sb O titanium dioxide (TiO zirconium dioxide (Zr O and manganese carbonate (MnCO are used as starting materials to obtain the Pb(Fe Sb )O -PbTiO -PbZrO ceramics containing manganese monoxide. These powdered materials were so proportioned that the final composition may comprise of various mol ratios x, y, and z of the basic composition with the manganese monoxide varying in iangle;

Tan 5 e (percent under an applied D.C. electric field After the ceramic discs stand for 24 hours, the electro ectric properties may be madein Tables 1 and 2 show typical results obtained. The basic inside the tr TABLE 1 Additive agent PbZrO; MnO (wt. k,- 2 percent) (percent) Qm KZLLLZZ 3 LLLL Z 4 2 LLL ZLLLL 2 1LLL ZLLLLL 111111 2 0 LLLL 1101 1111 52.14.

000 0000 0000 0000000 000000 00000 00000 0000 0000000 000000 00000000 0 3408 3297 1 34936 24180 4200 5541875 8167100 59985803 2934. mwwflu cw% NOZ WMU MH 33222 88900 $3333 6555444 898665 3 9765 8765 2221 2211 L 1 1 1 0000 0000000 000000 00000 00000 00000 0000000 000000 00000000 00 0000 47 35 4 899 2 480 g g 310 0512 8 46 3569 2898 m%mw%ww m wmwmmmm 50%29 14715 Q3%%% 341wu 8mm ZHNAW WW 281M0864 142:7 35618 1 1 1 1 1 1 1'1 1 1 1 1 1 1 1 1 Ll L 1 111 1 3 94 329 7 57 56352 8717542 863230 72722837 2 68 24 1 9629 1111 3 332 31322 5343333 656544 56665443 3221 1111 1 0 0. 0 00000 0000 0000 0000 0 3 .0 mwmm wm o 3 01 25 mmmw mmwmmmm mmmm m mmmwmmmw 015 0 1 5 0 1 123 3 000 0000 0 0 0 0 0000 00 0 0 0 0 00 0 0 000 000 000 777 77 00000 22222 55555 2222222 999999 1 111 11 888 00 000 M M4 88883 444 44 66666 5555555 444444 5 555 55 444 999 999 are press-molded into discs of 20 mm. in diameter at a pressure of 700 -kg./cm. and sinter'ed in an atmosphere of lead monoxide (PbO) for one hour at a temperature of 1260 to 1300 C. The resulting ceramic discs are 5 polished to a thickness of one millimeter, provided With silver electrodes .on both surfaces, and thereafter piezoelectrically activated through polarization treatment .for. one hour at 100 C. of 30 to 50 kv./cm.

mechanical coupling factor for the radial-mode vibration (k,)' and the mechanical quality factor (Q 'may be measured to evaluate the piezoelectric properties. Measurement of these piezoel k is calculated by the resonant toantiresonant frequency method. The dielectric constant (e) and the dielectric loss (tan 6) are also measured at a frequency of 1 kHz.

FIG. 1 by the points located M01 ratio of basic composition Pb(FBi/2sb1/2)O3 PbIiO;

having compositions shown in Table 2, in which a atom percent of lead (Pb) of the basic composition havic oxide (Fe 0 antimony sesquioxide 10 .(Sb O manganese carbonate. (MnCO and barium,

amount from 0.00 to 3.0 percent of weight as shown in Table "1. Furthermore, barium carbonate ('BaCO strontium carbonate (SrCO or calcium carbonate (CaCO may be added to the above starting materials to obtain ceramics ng the mol ratios x, y, and z of the Pb(Fe Sb )O' PbTIiO and PbZrO componentsis replaced by barium (Ba), strontium (Sr) or calcium (Ca) represented by Me in the table. Ferr strontium'or calcium carbonate (BaCO SrCO or CaCOg) are proportioned as calculated on the basis of ferric oxide (Fe O antimony pentoxide (Sb -O manganese monoxide (MnO), and barium, strontium or calcium oxide accordance with the IRE standard circuit. The value of (BaO, SrO or CaO), respectively.

The respective powders are mixed in a ball mill with distilled Water. The mixed powders are then subjected to filtrationfdrie'd, .crush'ed, presintered at 900 C. for one hour, and again crushed. Thereafter, the mixtures, with compositions of the specimens of Table 1 are shown in a small amount of distilled water being added thereto,

00 00000 0 000 55 5 5 5 22 22222 1111 1111 000 mmmm 11111 11111 0 0% 0%%%%%% %%%%00 00 00000 0000 0000 111 See tootnotee at end of table.

TABLE 1-Oont-i nued Additive M01 ratio of basic composition agent Pb(Fe1 2Sb1/2)0a PbTiO PbZrOa MnO (wt. k, Tan 5 No. I y 2 percent) (percent) Qm 6 (percent) NOTE:

manganese carbonate (M11003) as one of the starting materials.

As will be apparent from Table 1, markedly improved piezoelectric properties are obtained in working over the preferred range of MnO of about 0.1 to 1% by weight.

The specimens whose No. have a sole asterisk are not included within the scope of this invention.

In manufacture of the specimens with double asterisks, manganese-dioxide (M1102) is used instead 01 Moreover, it has been found that the superior piezoelectric properties as shown and mentioned are available TABLE 2 Basic composition MnO (wt. in Ten; 2: 1! z 11. Me percent) (percent) Qm e (percent) 0.05 0.47 0.48 0.02 Ga 0.00 64 240 750 1.8 0.05 0.47 0.48 0.02 Ga 0.10 39 540 780 1.0 0.05 0.47 0.48 0.02 Ga 0.50 53 1,200 580 1.3 0.05 0.47 0.48 0.02 Ga. 3.0 30 590 530 1.6

.05 0.41 0.54 0.10 Ga 0.00 62 190 1,380 2.2 .05 0.41 0.54 0.10 Ga 0.10 53 690 930 1.1 .05 0.41 0.54 0.10 Ga. 0.50 56 1,610 680 1.2 .05 0.41 0.54 0.10 Ga 3.0 29 670 550 2.0

.05 0.43 0.52 0.10 Sr 0.00 67 230 1,330 2.1 .05 0.43 0.52 0.10 St 0.10 45 790 900 1.0 .05 0.43 0.52 0.10 Sr 0.50 56 1,640 720 1.2 .05 0.43 0.52 0.10 Sr 3.0 33 730 580 1.8

.05 0.40 0.55 0.20 Sr 0.00 53 180 1,880 2.4 .05 0.40 0.55 0.20 Sr 0.10 32 670 1,270 1.3 .05 0.40 0.55 0.20 Sr 0.50 48 1,690 860 1.6 .05 0.40 0.55 0. 20 Sr 3.0 26 770 710 2.2

.05 0.47 0.48 0.05 Ba. 0.00 66 270 790 1.9 .05 0.47 0.48 0.05 Ba 0.10 45 780 820 1.3 .05 0.47 0.48 0.05 Ba 0.60 53 1,210 600 1.6 .05 0.47 0.48 0.05 Ba 3.0 36 480 610 1.9

.05 0.46 0.49 0.10 Ba 0.00 230 960 2.1 .05 0.46 0.49 0.10 Ba 0.10 51 720 1,020 1.1 .05 0.46 0.49 0.10 Ba 0.50 46 1,250 810 1.5 .05 0.46 0.49 0.10 Ba 3.0 38 530 580 2.0

Table 1 reveals that the incorporation of 0.10 to 3.0 wt. percent MnO to the basic compositions results in an increased or widely ranged value of k and sharply enhanced Q In other words, such incorporation results in an excellent material for use in the elements of ceramic filters, the transducer elements of mechanical filters or other fields where high or widely ranging k and large Q are both required.

FIG. 2 shows the relation between the content a of MnO and the resultant piezoelectric properties (k, and Q in specimens Nos. 8 to 14 of Table 1 as representative examples. It will be clearly seen from FIG. 2 that excellent piezoelectric properties are obtainable if the content of MnO lies within a range from 0.10 to 3.0 weight percent.

Where the Mn() content is less than 0.10 wt. percent, little improvement of piezoelectric properties is effected by incorporation of MnO. If the MnO content exceeds 3.0 wt. percent, Q decreases considerably and it becomes difiicult to obtain a uniform solid solution of the additive agent and the basic composition and to accomplish the polarization treatment. Thus the eifective range of the MuO content is defined from 0.10 to 3.0 wt. percent.

when the basic compositions represented by the formula ['Pb (Fe Sb [PbZIOflZ' where, x, y and z represent a set of mol ratios and x+y+z=1.00, and falling within the polygonal area A-B-C-D-E-F-G of FIG. 1 of the drawing, the sets of mol ratios x, y, and z of the vertices of this polygonal area are as follows:

9????99 coon-no oooog e 9. 99. 99 oemoacmow oococooe m It should be noted that the improvement made in the piezoelectric properties by incorporation of MnO clearly results from the presence of manganese ions. There are various known methods for producing manganese ions using as a starting material manganese oxide itself (such as MnO or MnO or some other manganese compound It will be apparent that the, starting materials to be.

used in the manufacture of the ceramics of this-invention are not limited to those used in the above examples. It may be observed that those oxides which are easily decomposed at elevated temperature to form the required compositions may be used instead of. the starting materials of the above examples. For example, Pb O may be substituted for PhD. Also, those salts such as oxalates or carbonates may be used instead of the oxides used in the cxamples, such salts being easily decomposed into the respective oxides at elevated temperatures. Otherwise, hydroxides of the same character as above, may be used instead of the oxides. Moreover, an excellent piezoelectric ceramic material having similar properties to the above examples is obtainable by preparing in advance separately the powdered material of each of Pb(Fe Sb )O PbTiO and PbZrO and of any starting material for MnO, and by using them as starting materials to be mixed subsequently.

It is usual for zirconium dioxide (ZrO available in the market to contain several percent of hafnium dioxide (HfO Accordingly, the ceramic compositions of this invention may contain small amounts of oxides or elements as existing in materials available in the market.

While there has been described what at present is believed to be the preferred examples of this invention, it will be obvious that various modifications can be made therein without departing from the scope of this invention and that this invention covers all the ceramic compositions as specified in the appended claims.

What we claim is:

1. Piezoelectric ceramics consisting essentially of a solid solution-of Pb (Fe Sb )O PbTiO and PbZrO and manganese oxide in the amount of 0.10 to 3.0 weight percent in the form of MnO, the composition of said solid solution being represented by the formula where x, y and z represent a set of mol ratios and x+y+z'=1.00, and falling Within the polygonal area A-B-C-D-E-F-G of .FIG. 1 of the drawing, the sets of mol ratios x, y and z of the'vertices of said polygonal area being as follows: I

P PPP commoners 00000000 N References Cited UNITED STATES PATENTS 3,268,453 8/1966 Ouchi et al. 25262.9 3,372,121 .3/1968 Banno 252-62.9 3,424,686 1/1969 Ouchi et al. 252-629 3,463,732 8/1969 Banno et a1 252-629 3,487,019 12/1969 Tsubouchi et al. 25262.9'

TOBIAS E. LEVOW, Primary Examiner J. COOPER, Assistant Examiner US. Cl; X.R. 10639 R 

